That's assuming that you don't have to pop all of your spell slots to get through the 8 hour work day. The 8 hour work day was chosen pretty precisely to be exactly exhausting enough in a menial labor factory assembly job that you return home with very little energy for anything else. If you presume your job is more (creatively, socially) taxing than "repeatedly doing the same task in an assembly" line, it's very easy to assume most jobs today are more exhausting in 8 hour shifts than what that work week was first established for.

You may have 6 hours of time left, but that doesn't mean you have 6 hours of energy reserves left to socialize or otherwise. (Clearly many people spend their evenings in low effort activities like watching TV on weeknights, too.)